For purposes of convenience and economics, it is often desirable to employ switches in optical networks, so that either a single optical signal can be shared between two or more users or a single user can choose from a variety of optical signals without the added expense and complexity of installing additional hardware. In particular, one-by-four fiber optical switch is used to change the path of an optical signal between a single input optical fiber connected to a transmitting location and four different output optical fibers connected to receiving locations, thereby allowing four different users to access an optical signal originating from a single source. Similarly, an output common one-by-four fiber optical switch is used to change the path of an optical signal between four different input optical fibers connected to transmitting locations and a single output optical fiber connected to a receiving location, thereby allowing a single user to access four different optical signals.
In optical fiber switches, either multi-mode fiber or single-mode fiber can be used. Regardless of what type of fiber is used, it has always been very difficult to align optical paths when bare fiber is used. Because fiber cores are so small, a misalignment of a few micrometers can cause large insertion losses (i.e., the loss in signal transmission). This is especially true when using single-mode fiber.
This misalignment problem has been addressed to some extent in the prior art through the use of a Grade Refractive Index (GRIN) lens. The GRIN lens makes the fiber act as if its core diameter has been enlarged to the size of the GRIN lens diameter, thereby making the fiber core diameter behave as if it was at least ten to one-hundred times larger. As a result, insertion losses will be minimized when there is a few micrometers of misalignment between the optical signal from the input fiber to the output fiber. Inherent misalignments cannot be corrected through the use of a GRIN lens.
Currently, there are two different technologies used to make optical fiber switches (exclusive of the integrated optic switch). A first is known as moving fiber. In this technology, either the input optical fibers (or the output optical fibers) are actually reoriented to switch the optical signal between outputs, or vice versa. The second is known as moving prism or mirror. In this technology, the refractive medium (i.e., the prism) or the mirror is reoriented to switch the optical signal between outputs while the fibers do not move. These prior art technologies, however, have suffered from unacceptable insertion losses and low stability (e.g. alignment problems).
An example of an optical system that uses a moving reflector assembly is disclosed in U.S Pat. No. 5,436,986 and co-pending application, U.S. Ser. No. 08/451,527, by the same inventor as this application. Both are hereby incorporated by reference in their entirety.